Japanese Patent Application Publication No. 2013-48230 A (hereinafter referred to as Patent Literature 1) discloses an RC-IGBT. This RC-IGBT includes an IGBT structure configured with an n-type emitter region, a p-type body region, an n-type drift region, an n-type collector region, a trench gate electrode, and the like, and the p-type body region also serves as an anode region to provide a diode structure as well. In this RC-IGBT, an n-type barrier region is formed under the body region, which also serves as the anode region, and an n-type pillar region that connects the barrier region and a front surface electrode (which serves both as an emitter electrode and as an anode electrode) is formed. The pillar region is formed in a spacing between adjacent gate trenches. In this RC-IGBT, a potential of the barrier region is maintained at a potential closer to a potential of the front surface electrode, and hence this makes it difficult for a diode configured with a pn junction between the body region and the barrier region to be turned on. This diode is turned on when the potential of the front surface electrode is further raised. The RC-IGBT in Patent Literature 1 utilizes the barrier region and the pillar region to suppress a flow of holes from the p-type body region into the n-type barrier region and the n-type drift region, and suppress a reverse recovery current of the diode.
Japanese Patent Application Publication No. 2008-21930 A (hereinafter referred to as Patent Literature 2) discloses a semiconductor device to which a dummy trench is added, in addition to a gate trench. In this semiconductor device, a pair of the dummy trenches is provided in a spacing between the adjacent gate trenches. A dummy electrode in each of the dummy trenches is insulated from a gate electrode in the gate trench, and connected to a source potential. In this semiconductor device, a pn diode configured with a p-type body region and an n-type drain region is formed in a spacing between the gate trench and the dummy trench. Moreover, there is formed, between the pair of the dummy trenches, an n-type region that is connected to the drift layer and Schottky-connected to a front surface electrode (which serves both as a source electrode and as an anode electrode). In this semiconductor device, the n-type region allows the drift region and the front surface electrode to be in Schottky-contact with each other, and hence a reverse recovery current of the pn diode is suppressed.